Cold operation mode control for an ivt

ABSTRACT

A transmission includes an electro-hydraulic controller that includes redundancy in the hydraulic circuit that permits single fault failures to be compensated for by changing the flow path of hydraulic fluid to bypass the single fault failure. The redundancy results in the ability of the transmission to maintain full operation in all modes.

CROSS-REFERENCE TO RELATED U.S. PATENT APPLICATION

This present application claims priority under 35 U.S.C. §119(e) to U.S.Provisional Patent Application Ser. No. 61/660,666, entitled “REDUNDANTVARIATOR CONTROL FOR AN IVT,” which was filed on Jun. 15, 2012, theentirety of which is hereby incorporated by reference.

TECHNICAL FIELD

The present invention relates generally to fault responses in amulti-mode automatic transmission that includes a toroidal tractiondrive including a variator. More specifically, the present inventionrelates to control system for bypassing faults in the multi-modeautomatic transmission to permit continued operation of the multi-modeautomatic transmission in single fault conditions.

BACKGROUND

In some vehicle transmissions, a ratio varying unit (“variator”) is usedto provide a continuous variation of transmission ratio rather than aseries of predetermined ratios. These transmissions may be referred toas continuously variable transmissions, infinitely variabletransmissions, toroidal transmissions, continuously variabletransmissions of the full toroidal race-rolling traction type, orsimilar terminology. In such transmissions, the variator is coupledbetween the transmission input and the transmission output via gearingand one or more clutches. In the variator, torque is transmitted by thefrictional engagement of variator disks and rollers separated by atraction fluid.

The variator torque is controlled by a hydraulic circuit, which includeshydraulic actuators (i.e., pistons) that apply an adjustable force tothe rollers. The force applied by the hydraulic actuator is balanced bya reaction force resulting from the torques transmitted between thesurfaces of the variator disks and the rollers. The end result is thatin use, each roller moves and precesses to the location and tilt anglerequired to transmit a torque determined by the force applied by thehydraulic actuators. A difference in the forces applied to the rollerschanges the rollers' tilt angle and thus, the variator ratio. A changein the rollers' tilt angle thus results not only in a net torque at thetransmission output but could also result in a change in torquedirection. The direction of the torque output determines whether thetorque application is positive or negative.

SUMMARY

The present application discloses one or more of the features recited inthe appended claims and/or the following features which, alone or in anycombination, may comprise patentable subject matter:

According to an aspect of the present disclosure, an electro-hydrauliccontroller for a multi-mode transmission including a continuouslyvariable transmitter operating in tandem with a countershaft assembly anelectro-hydraulic system with a variator control that boosts pressure tothe variator while the transmission operates in a cold mode.

Additional features, which alone or in combination with any otherfeature(s), including those listed above and those listed in the claims,may comprise patentable subject matter and will become apparent to thoseskilled in the art upon consideration of the following detaileddescription of illustrative embodiments exemplifying the best mode ofcarrying out the invention as presently perceived.

BRIEF DESCRIPTION OF THE DRAWINGS

The detailed description particularly refers to the accompanying figuresin which:

FIG. 1 is a block diagram of a vehicle that includes a drive unit, atransmission receiving rotational input from the drive unit, thetransmission converting the rotational input from the drive unit andapplying an output to a vehicle load to control the speed and directionof travel of the vehicle under varying conditions;

FIG. 2 is a diagrammatic representation of a variator of thetransmission of FIG. 1, the variator operable as a continuously variablerotational transmitter and operable to vary a ratio of rotational inputto rotational output when the transmission is operated;

FIG. 3 is a functional block diagram of an electro-hydraulic controllerof the transmission;

FIG. 4 is a block diagram of components of a variator control of theelectro-hydraulic controller of the transmission;

FIG. 5 is a block diagram of components of a mode control of theelectro-hydraulic controller of the transmission;

FIG. 6 is a state diagram showing possible states of theelectro-hydraulic controller when a single fault is experienced in theelectro-hydraulic controller;

FIG. 7 is a schematic of a portion of the hydraulic circuit of thetransmission including a main pump; lubrication sub-circuits; cooling,filtering, relief and regulation of the hydraulic circuit;

FIG. 8 is a schematic of the variator control portion of the hydrauliccircuit of the transmission;

FIG. 9 is a schematic of the mode control portion of the hydrauliccircuit of the transmission showing a first mode trim valve in an activestate;

FIG. 10 is a schematic of a portion of the hydraulic circuit of thetransmission associated with the control of the variator;

FIG. 11 is a schematic of the remainder of the hydraulic circuitassociated with the control of the variator not shown in FIG. 10;

FIG. 12 is a schematic of the mode trim control section of the modecontrol portion of the hydraulic circuit of the transmission showingboth mode trim valves in an active state;

FIG. 13 is a schematic of the mode trim control section of the modecontrol portion of the hydraulic circuit of the transmission showing asecond mode trim valve in an active state;

FIG. 14 is a schematic of the mode logic control section of the modecontrol portion of the hydraulic circuit of the transmission showing asecond mode logic valve in a stroked state;

FIG. 15 is a schematic of the mode logic control section of the modecontrol portion of the hydraulic circuit of the transmission showingboth mode logic valves in a stroked state;

FIG. 16 is a schematic of the mode logic control section of the modecontrol portion of the hydraulic circuit of the transmission showing afirst mode logic valve in an active state;

FIG. 17 is a schematic of the variator logic control section of thevariator control portion of the hydraulic circuit of the transmissionshowing a first variator logic valve in a stroked state;

FIG. 18 is a schematic of the variator logic control section of thevariator control portion of the hydraulic circuit of the transmissionshowing a second variator logic valve in a stroked state;

FIG. 19 is a schematic of the variator logic control section of thevariator control portion of the hydraulic circuit of the transmissionshowing both the first variator logic valve and the second variatorlogic valve in a de-stroked state;

FIG. 20 is a schematic of another embodiment of a mode logic controlsection of the mode control portion of the hydraulic circuit of thetransmission showing both three mode logic valves with none of the threevalves in a stroked state;

FIG. 21 is a schematic of another embodiment of a mode logic controlsection of the mode control portion of the hydraulic circuit of thetransmission showing both three mode logic valves with the second andthird of the three valves in a stroked state;

FIG. 22 is a schematic of another embodiment of a mode logic controlsection of the mode control portion of the hydraulic circuit of thetransmission showing both three mode logic valves with the second of thethree valves in a stroked state;

FIG. 23 is a table showing a system response to a single point failurewhen a first embodiment of transmission is operating under normalconditions, hydraulic fault conditions shown in the left column, desiredtransmission states shown across the top of the remaining columns, andthe respective response state shown in the table;

FIG. 24 is a table showing a system response to a single point failurewhen a first embodiment of transmission is operating under coldoperating conditions, hydraulic fault conditions shown in the leftcolumn, desired transmission states shown across the top of theremaining columns, and the respective response state shown in the table;

FIG. 25 is a table showing a system response to a single point failurewhen a second embodiment of transmission is operating under normalconditions, hydraulic fault conditions shown in the left column, desiredtransmission states shown across the top of the remaining columns, andthe respective response state shown in the table;

FIG. 26 is a table showing a system response to a single point failurewhen a second embodiment of transmission is operating under coldoperating conditions, hydraulic fault conditions shown in the leftcolumn, desired transmission states shown across the top of theremaining columns, and the respective response state shown in the table;

FIG. 27 is a diagrammatic representation of a portion of the controlcircuit of the first embodiment of transmission; and

FIG. 28 is a diagrammatic representation of a portion of the controlcircuit of the second embodiment of transmission.

DETAILED DESCRIPTION OF THE DRAWINGS

For the purposes of promoting an understanding of the principles of theinvention, reference will now be made to a number of illustrativeembodiments shown in the attached drawings and specific language will beused to describe the same.

While the concepts of the present disclosure are susceptible to variousmodifications and alternative forms, specific exemplary embodimentsthereof have been shown by way of example in the drawings and willherein be described in detail. It should be understood, however, thatthere is no intent to limit the concepts of the present disclosure tothe particular forms disclosed, but on the contrary, the intention is tocover all modifications, equivalents, and alternatives falling withinthe spirit and scope of the invention as defined by the appended claims.

References in the specification to “one embodiment”, “an embodiment”,“an example embodiment”, etc., indicate that the embodiment describedmay include a particular feature, structure, or characteristic, butevery embodiment may not necessarily include the particular feature,structure, or characteristic. Moreover, such phrases are not necessarilyreferring to the same embodiment. Further, when a particular feature,structure, or characteristic is described in connection with anembodiment, it is submitted that it is within the knowledge of oneskilled in the art to effect such feature, structure, or characteristicin connection with other embodiments whether or not explicitlydescribed.

In one embodiment, a drive train 10 of a vehicle 8 includes a drive unit12 and a transmission 14 configured to drive a vehicle load 18 as shownin FIG. 1. The transmission 14 includes an electro-hydraulic controller16 coupled to an engine control module (ECM) 80 of the drive unit 12 tocoordinate the operation of the drive unit 12 and the transmission 14.In some embodiments, the drive train 10 may include other componentscommonly found in drive trains but not illustrated in FIG. 1 in order toincrease clarity of the present description.

The drive unit 12 is illustratively a diesel internal combustion engine.However, in other embodiments, the drive unit 12 may be embodied as aspark-ignition type internal combustion engine (i.e. gasoline engine), ahybrid engine-electric motor combination, or another source ofrotational power. The drive unit 12 has drive unit output shaft 20 thatprovides rotational power to the transmission 14.

The transmission 14 is operable to transmit the rotational power fromthe drive unit 12 to the vehicle load 18 at various transmission ratios.The transmission ratio provided by the transmission 14 is modified bythe electro-hydraulic controller 16. The electro-hydraulic controller 16is configured to modify the transmission ratio so that the drive unit 12operates at an optimized set of parameters corresponding to the vehicleload 18 and speed of the vehicle 8.

The transmission 14 illustratively includes an input clutch 46, avariator 22, and a countershaft assembly 70 with two clutches 156, 158operable to change the ratio of the transmission 14 under the control ofthe electro-hydraulic controller 16. The input clutch 46 is configuredto be stroked to transfer rotation to the variator 22 from the driveunit output shaft 20. The transmission 14 is embodied as a continuouslyvariable countershaft transmission unit as is known in the art. In otherembodiments, the transmission 14 may be an infinitely variabletransmission. The ratio through the transmission 14 is adjustable byselectively energizing the clutches 156, 158 in the countershaftassembly 70 and by varying the ratio of an input 32 to the variator 22to an output 38 of the variator 22 as described below. The variator 22is an infinitely variable rotational transmitter that is operable tovary the ratio through the variator 22 under the control of theelectro-hydraulic controller 16. The countershaft assembly 70 receivesrotational output from an output 38 of the variator 22 and acts as arotational transmitter to transmit the rotation from the output 38 ofthe variator 22 to the vehicle load 18. In the illustrative embodiment,the countershaft assembly 70 includes at least one epicyclic gear setthat may, under certain conditions, reverse the direction of output fromthe variator 22. Thus, the transmission 14 is operable to receiverotational input from the drive unit 12 and convert that rotationalinput to positive or negative rotational output to the vehicle load 18,including operating at a geared neutral condition.

As illustratively shown in FIG. 2, the variator 22 includes an inputshaft 32 that is selectively coupleable to the drive unit output shaft20 through the input clutch 46 of the transmission 14. The variator 22includes a first input race 34 and a second input race 36, each of whichis coupled to the input shaft 32 to rotate with the input shaft 32 abouta rotation axis 250. Each of the races 34 and 36 is a disk centered onthe axis 250. The input race 34 is formed to include a race surface 54that is engaged by three rollers 62 a, 62 b, and 62 c (not shown in FIG.2). Similar to input race 34, input race 36 is formed to include a racesurface 60 which cooperates with three rollers 64 a, 64 b, 64 c (notshown in FIG. 2). As will be discussed in further detail below, theengagement between the race surfaces 54 and 60 and the respectiverollers 62 a, 62 b, 62 c, 64 a, 64 b, 64 c does not require contactbetween the rollers 62 a, 62 b, 62 c, 64 a, 64 b, 64 c and therespective race surfaces 54 and 56.

As the input shaft 32 rotates about the axis 250, the input races 34 and36 rotate with the input shaft 32 and the engagement with the rollers 62a, 62 b, 62 c, 64 a, 64 b, 64 c transfers rotation of the races 34 and36 to the respective rollers 62 a, 62 b, 62 c, 64 a, 64 b, 64 c. Each ofthe rollers 62 a, 62 b, 62 c, 64 a, 64 b, 64 c rotates about arespective axis 52 a, 52 b, 52 c (not shown) and 50 a, 50 b, and 50 c(not shown). As will be described in further detail below, each of theaxes 52 a, 52 b, 52 c, 50 a, 50 b, 50 c are pivotable to thereby changethe position of the respective rollers 62 a, 62 b, 62 c, 64 a, 64 b, 64c relative to the input races 34 and 36. It should be understood thatthe rotation of the rollers 62 a, 62 b, 62 c, 64 a, 64 b, 64 c iscontrolled such that each of the rollers 62 a, 62 b, 62 c, 64 a, 64 b,64 c rotates at substantially the same speed as the orientation of theaxes 52 a, 52 b, 52 c, 50 a, 50 b, 50 c is coordinated as describedherein.

The variator 22 further includes an output 38 which includes an outputrace 44 supported on the input shaft 32 on roller bearings 40 so thatthe output 38 is supported on the input shaft 32 but is rotatablerelative to the input shaft 32. Illustratively, the output 38 is formedto include a number of gear teeth 26 positioned about the periphery ofthe output race 44, with the gear teeth 26 configured transfer outputrotations to a complementary gear coupled to the countershaft assembly70 of the transmission 14. It should be understood that the output 38may take other forms and may be fixed to the input shaft 32 in otherembodiments.

The variator 22 includes an endload assembly 134 that includes a housing42. The endload assembly 134 includes a endload chamber 66 that ispressurized to apply a force to the input race 36 that acts on therollers 62 a, 62 b, 62 c, 64 a, 64 b, 64 c and output race 44 to clampthe rollers 62 a, 62 b, 62 c, 64 a, 64 b, 64 c and output race 44between the input race 36 and the input race 34. The clamp force betweenthe input race 36 and the input race 34 is variable as will bedescribed. In the illustrative embodiment, the input race 34 is fixed tothe input shaft 32 and the input race 36 is movable to increase theclamp load.

The input race 36 forms part of the endload assembly 134 and is movablerelative to the input shaft 32 along axis 250 in a direction indicatedby an arrow 68. An endload chamber 66 is pressurized with hydraulicfluid to apply a force to the input race 36 urging it in the directionof arrow 68. The input race 36 is engaged with the input shaft 32through a splined connection 78. The splined connection 78 includes theengagement of a number of splines 180 formed in the input race 36 whichengage a number of splines 182 on the input shaft 32. Rotation istransferred to the input race 36 from the input shaft 32 through thesplined connection 78, but the input race 36 is permitted to move alongthe input shaft 32 when the endload chamber 66 is pressurized. It shouldbe understood that FIG. 2 is a diagrammatic representation of thevariator 22. In actual operation, the movement of the race 36 will bevery slight and only of sufficient magnitude to transfer the pressure ofthe hydraulic fluid in the endload chamber 66 to the rollers 62 a, 62 b,62 c, 64 a, 64 b, 64 c, the output 38, and the first input race 34. Themagnitude of pressure in the endload chamber 66 varies the clamp forceapplied to the variator 22 to reduce or eliminate relative movementbetween the rollers 62 a, 62 b, 62 c, 64 a, 64 b, 64 c, and the racesurfaces 54, 56, 58, 60. Those of ordinary skill in the art willrecognize that a greater clamping force will tend to increase therolling resistance between the rollers 62 a, 62 b, 62 c, 64 a, 64 b, 64c, and the race surfaces 54, 56, 58, and 60. As such, it is necessary tolimit the clamping force to only that which is necessary to limitrelative movement between the rollers 62 a, 62 b, 62 c, 64 a, 64 b, 64c, and the race surfaces 54, 56, 58, and 60. The clamping force willvary depending on the load variation between the output 38 and the inputshaft 32.

Referring now to FIG. 3, the electro-hydraulic controller 16 includestwo functions: a variator control 120 and a mode control 122. Thevariator control 120 is operable to control operation of the variator 22under changing operating conditions. Control of the variator 22 by thevariator control 120 is accomplished by a variator logic section 124 anda variator trim section 126. The variator control 120 controls theposition of the axes 50 a, 50 b, 50 c, 52 a, 52 b, 52 c to control theratio transmitted through the variator 22 from input shaft 32 to theoutput 38. Under certain conditions, the variator control 120 appliespressure in a first direction, depending on the direction of torquebeing applied to the output 38 of the variator 22. As is known in theart, a variator, such as variator 22 operates in a single operationaldirection and a negative torque condition must be addressed in thevariator 22 to prevent rotation of the variator 22 in a negativedirection, which might cause damage to the variator 22.

The variator trim section 126 controls the magnitude of pressure appliedto six cylinders 184 a, 184 b, 184 c, 186 a, 186 b, and 186 c (shown inFIG. 10) each of which is associated with a corresponding axis 50 a, 50b, 50 c, 52 a, 52 b, 52 c to vary the position of the axes 50 a, 50 b,50 c, 52 a, 52 b, 52 c to thereby change the ratio of the variator 22.By varying the pressure applied to the cylinders 184 a, 184 b, 184 c,186 a, 186 b, and 186 c (shown in FIG. 10), the variator trim section126 overcomes resistance to movement of the axes 50 a, 50 b, 50 c, 52 a,52 b, 52 c to thereby change the position of the rollers 62 a, 62 b, 62c, 64 a, 64 b, 64 c. As described above, the position of the rollers 62a, 62 b, 62 c, 64 a, 64 b, 64 c defines the ratio transmitted throughthe variator 22. Application of additional pressure causes the rollers62 a, 62 b, 62 c, 64 a, 64 b, 64 c to move toward a new position untilthe resistance of movement of the rollers 62 a, 62 b, 62 c, 64 a, 64 b,64 c is in equilibrium with the pressure applied to the cylinders 184 a,184 b, 184 c, 186 a, 186 b, and 186 c as determined by theelectro-hydraulic controller 16. When equilibrium is reached, the ratiothrough the variator 22 is maintained until a change in torque isapplied to the output 38 of the variator 22, at which time theequilibrium will be lost and the electro-hydraulic controller 16 willrespond to the loss of equilibrium by moving the cylinders. 184 a, 184b, 184 c, 186 a, 186 b, and 186 c to a new position to reach a newequilibrium.

The variator 22 of the illustrative embodiment is operates as acontinuously variable transmitter (CVT). In other embodiments, otherconfigurations of CVT may be substituted and still be within the scopeof the present disclosure. Other CVT's with hydraulically actuatedvariation are susceptible to the application of the controls of thepresent disclosure; to the extent such systems are subject to singlefault conditions.

The electro-hydraulic controller 16 includes a processor 72 that is incommunication with the ECM 80 of the drive unit 12 and a control circuit76 that controls the electrical components of the electro-hydrauliccontroller 16. The processor 72 is operable to receive information fromthe ECM 80 indicative of the desired operation of the vehicle 8, such asa speed input from a foot pedal, engine speed, desired transmissionoperating mode, or other information. The information may be provided asdiscreet inputs or may be provided as serial data or network messages.For example, the electro-hydraulic controller 16 may communicate to withthe ECM 80 through a serial interface such as an I²C, SPi, LIN bus, orother similar serial interface. In other embodiments, theelectro-hydraulic controller 16 may communicate with the ECM 80 over acontroller area network (CAN) or other higher level network.

The processor 72 accesses instructions in a memory device 74 andprocesses the instructions to control operation of the control circuit76 and associated components as will be described. The control circuit76 includes devices necessary to convert digital instructions from theprocessor 72 to outputs usable by the components of theelectro-hydraulic controller 16. For example, the control circuit 76 mayinclude relays or other logical devices which respond to a digitalsignal from the processor to operate any analog components of theelectro-hydraulic controller 16. Similarly, the control circuit 76 mayinclude filters, amplifiers, and other devices necessary to convertanalog signals from pressure sensors to a digital signal for theprocessor 72. In addition, the control circuit 76 includes speed sensors(not shown) that determine the input speed to the transmission 14 whichis determined by measuring the speed of the drive unit output shaft 20;at the output 38 of the variator 22, and at an output shaft 21 of thetransmission 14. The processor 72 utilizes the speed information as partof the logical operation of the electro-hydraulic controller 16 todetermine the torque applied to the output 38 of the variator 22 to makedecisions regarding appropriate operating conditions for thetransmission 14.

As shown in FIG. 4, the variator logic section 124 comprises threevalves, a first variator logic valve 130, a second variator logic valve132, and a variator boost valve 148. Each of the variator logic valves130, 132, and 148 are operatively coupled to the processor 72 throughthe control circuit 76 and are operated under the control of theprocessor 72. As will be discussed in further detail below, the firstvariator logic valve 130, and the second variator logic valve 132,cooperate to control the direction of flow of pressurized hydraulicpressure to the cylinders 184 a, 184 b, 184 c, 186 a, 186 b, and 186 c.The variator boost valve 148 is operable to provide a pressure boost tothe variator trim control 126 when the transmission 14 is operating coldand valve 142 is in a fault condition to apply a boosted pressure to thehydraulic cylinders 184 a, 184 b, 184 c, 186 a, 186 b, and 186 c and theendload chamber 66. Each of the first variator logic valve 130, thesecond variator logic valve 132, and the variator boost valve 148 havetwo different logical states to thereby change the flow path ofhydraulic fluid. The logic states of each of the valves 130, 132, and148 change in response to changing operating conditions of thetransmission 14. In addition, each valve 130, 132, and 148 has arespective pressure sensor 136, 138, and 140 associated with arespective variator logic valve 130, 132, and 148. Each sensor 136, 138,and 140 is positioned to sense the presence of pressure in the circuitto confirm that the each valve 130, 132, and 148 is operating asexpected. The pressure sensors 136, 138, 140 are operatively coupled tothe processor 72 through the control circuit 76 and are operable toprovide a signal indicative of the pressure sensed by each sensor toprocessor 72. The pressure sensors 136, 138, and 140 operate as faultdetectors to determine if hydraulic fluid is flowing as expected.Because the valves 130, 132, and 148 are operated open-loop, i.e.without direct feedback from the valve 130 132, 148 to confirm that thevalve has responded to a signal to energize, the actual position of thevalve is not known by the processor 72 of the electro-hydrauliccontroller 16. The pressure sensors 136, 138, and 140 provide feedbackto the electro-hydraulic controller 16 to confirm the variator control120 is operating as expected by confirming that the variator logicvalves 130, 132 and 148 are stroked or de-stroked as expected by theprocessor 72. In the illustrative embodiment, the pressure sensors 136,138, and 140 are pressure switches that activate once a minimum pressurehas been applied to the switch. In other embodiments, the pressuresensors 136, 138, and 140 may be embodied as transducers providing avariable signal indicative of the pressure in the system.

The variator trim section 126 includes a first variator trim valve 142and a second variator trim valve 144. Each of the variator trim valves142 and 144 has an associated pressure sensor 146 and 148. The pressuresensors 146 and 148 operate to provide feedback to the processor 72electro-hydraulic controller 16 as to the operation of the respectivevariator trim valves 142 and 144 and the pressure applied to thecylinders 184 a, 184 b, 184 c, 186 a, 186 b, and 186 c. The variatortrim valves 142 and 144 respond to changes in an input signal to varythe pressure output by the variator trim valves 142 and 144 and appliedto the cylinders 184 a, 184 b, 184 c, 186 a, 186 b, and 186 c. In theillustrative embodiment, the pressure sensors 146 and 148 are pressureswitches that activate once a minimum pressure has been applied to theswitch. In other embodiments, the pressure sensors 146 and 148 may beembodied as transducers providing a variable signal indicative of thepressure in the system.

The mode control 122 has two functions including a mode logic section150 and a mode trim control 152 which cooperate to control the operationof the input clutch 46, a first mode clutch 156, and a second modeclutch 158. The input clutch 46 is used to control the transfer ofrotational input from the drive unit output shaft 20 to the transmission14. The first mode clutch 156 and second mode clutch 158 are used tocontrol the path that rotation is transferred from the variator 22through the countershaft assembly 70 to control the ratio and directionof rotation transferred from the transmission 14 to the vehicle load 18.The mode logic section 150, under the control of the processor 72 of theelectro-hydraulic controller 16, varies the flow path of pressurizedhydraulic fluid to the first mode clutch 156 and the second mode clutch158 to energize or de-energize the first mode clutch 156 and the secondmode clutch 158 depending on operating conditions, faults, and userinputs.

The mode logic section 150 includes a first clutch logic valve 160 and asecond clutch logic valve 162 which cooperates to control the fluid pathfor hydraulic fluid to the first mode clutch 156, second mode clutch158, and input clutch 46 as will be described in further detail below.Each clutch logic valve 160 and 162 has an associated pressure sensor164 and 166, respectively. The pressure sensors 164 and 166 functionsimilarly to the pressure sensors 136, 138, and 140 described herein inthat they provide a feedback signal to the processor 72 to confirm thatthe valves 160 and 162 are operating as expected.

The mode trim control 152 includes a first mode trim valve 168 and asecond mode trim valve 170 that control the pressure fed to the firstmode clutch 156, second mode clutch 158, and the input clutch 46 throughthe mode logic section 150. A pressure sensor 172 is associated withfirst mode trim valve 168 and a pressure sensor 174 is associated withsecond mode trim valve 170 with each of the pressure sensors 172 and 174operable to determine if the flow path through valves 168 and 170 is asexpected by the processor 72.

Referring now to FIG. 27, the control circuit 76 includes a first driver600 that is operable to provide sufficient power to the first variatortrim valve 142 and the first mode trim valve 168. The driver 600includes circuitry to control the operation of the solenoids of thevalves 142 and 168 under the control of the processor 72. The driver 600may experience a fault that prevents proper operation of valves 142 and168, but the electro-hydraulic controller 16 is responsive to a fault inthe driver 600.

A second driver 602 is operable to power the second variator trim valve144 and the second mode trim valve 170 as well as the boost valve 148. Athird driver 604 is operable to power the first variator logic valve 130and the first mode logic valve 160. A fourth driver 606 is operable topower the second variator logic valve 132 and the second mode logicvalve 162.

The detailed operation of the hydraulic circuit of the electro-hydrauliccontroller 16 is best understood with reference to the operationalstates of the electro-hydraulic controller 16. Each operational state ofthe electro-hydraulic controller 16 is referenced by a four part statename that identifies the operational state of each of a number ofaspects of the transmission 14.

In a first embodiment of transmission 14, the first aspect is defined byan operational state of the variator 22. “C” indicates that the variator22 is operating in a cold condition. When the transmission 14 operatescold the viscosity of the hydraulic fluid between the rollers 62 a, 62b, 62 c, 64 a, 64 b, 64 c and the race surfaces 54, 56, 58, and 60 ishigher than under normal, hot operating conditions. Theelectro-hydraulic controller 16 compensates for this difference whilethe transmission 14 warms up. “H” indicates that the variator 22 isoperating in a normal, hot condition. “1” indicates that the firstvariator trim valve 142 is in a fault condition. Thus, there are threedifferent variator operational states identified by the first aspect.

The second aspect of the state name is defined by the clutch operationalstate. There are four clutch operational states with “NL” indicatingthat the clutch state is Normal Low; “NH” indicating that the clutchstate is Normal High; “FL” indicating that the clutch state is FaultLow; and “FH” indicating that the clutch state is Fault High.

The third aspect of the state name is defined by the mode state withfive different mode operational states. The absence of a character inthe state name indicates that the mode operational state is Neutral. A“0” indicates that the transmission 14 mode is Mode 0. A “1” indicatesMode 1; a “2” indicates Mode 2; and a “T” indicates that thetransmission is in Transition between Mode 1 and Mode 2, meaning thatboth Mode 1 and Mode 2 are active.

The final part in the state name indicates torque direction applied tothe variator 22 by the vehicle load 18 through the countershaft assembly70. The torque direction may change depending on whether the vehicle 8is accelerating or operating on an upward incline as compared todeceleration or operating on a downward incline. “0” indicates thatthere is no torque applied, while “−” indicates a negative torquedirection. “+” indicates a positive torque direction, while “FR”indicates that the transmission is operating in a fixed ratio, bypassingthe variator 22 and using the countershaft assembly 70 only to transferrotation through the transmission 14. The FR state of the torque occursduring the Transition mode.

Table 1 below lists the states for the transmission 14 using the statename convention described above.

TABLE 1 Normal States Mode - Torque Direction Cold Hot Neutral Start CNL 0 0 H NL 0 0 Mode 1 - Negative Torque C NL 1 − H NL 1 − Mode 1 -Positive Torque C NL 1 + H NL 1 + Mode Transition C NH T FR H NH T FRMode 2 - Negative Torque C NH 2 − H NH 2 − Mode 2 - Positive Torque C NH2 + H NH 2 +

Table 2 shows the state names that are associated with a failure of thefirst variator trim valve 142

TABLE 2 142 Fault States Mode - Torque Direction Cold Hot Neutral Start1 NL 0 0 1 NL 0 0 Mode 1 - Negative Torque 1 NL 1 − 1 NL 1 − Mode 1 -Positive Torque 1 NL 1 + 1 NL 1 + Mode Transition 1 NH T FR 1 NH T FRMode 2 - Negative Torque 1 NH 2 − 1 NH 2 − Mode 2 - Positive Torque 1 NH2 + 1 NH 2 +

Each state of the transmission can be defined by a state logic key whichis a binary definition of the logic state of each of the valves 142,144, 168, 170, 130, 132, 160, 162, and 148, in order. The variator trimvalves 142 and 144 each have two states, “T” for the trim state and “0”for an open state. In the trim state, the 142 or 144 is operated by theprocessor 72 based on the torque sensed by the electro-hydrauliccontroller 16 so that the proper pressure is applied to the cylinders184 a, 184 b, 184 c, 186 a, 186 b, and 186 c.

The proper operating state of the electro-hydraulic controller 16 isconfirmed by comparing the status of the various pressure sensors 136,138, 164, 166, 140, 278, 286, 146, 148, and 176 to expected values. Thestates of the pressure sensors 136, 138, 164, 166, 140, 278, 286, 146,148, and 176 are defined with a binary status of “1” for the pressuresensor being “on” or active receiving an acceptable pressure signal, and“0” for being “off” or receiving no pressure signal, or a pressuresignal that is too low. As described above, the pressure sensors 136,138, 164, 166, 140, 278, 286, 146, 148, and 176 in the illustrativeembodiment are pressure switches that activate when a predeterminedpressure is applied to the sensor. In other embodiments, the pressuresensors 136, 138, 164, 166, 140, 278, 286, 146, 148, and 176 may detectvariations in pressure and transmit a signal to the processor 72 that isindicative of the actual pressure being applied to the respectivesensor. When the pressure sensors 136, 138, 164, 166, 140, 278, 286,146, 148, and 176 detect variations in pressure, sufficient pressureapplied to the pressure sensor is considered a “1” or “on” condition bylogic of the electro-hydraulic controller 16. The normal operatingstates of the pressure sensors of the electro-hydraulic controller 16are shown in Table 3 below.

TABLE 3 Normal Pressure Sensor States STATE NAME 136 138 164 166 140 278286 146 148 176 C NL 0 0 0 0 0 0 0 1 0 0 1 0 C NL 1− 0 0 0 0 0 1 1 0 1 0C NL 1+ 0 1 0 0 0 1 1 0 1 0 C NH T FR 0 0 0 1 0 1 1 0 1 0 C NH 2+ 0 0 01 0 0 1 0 1 0 C NH 2− 0 1 0 1 0 0 1 0 1 0 H NL 0 0 1 1 0 0 0 1 0 1 0 0 HNL 1− 1 1 0 0 0 1 1 1 0 0 H NL 1+ 1 0 0 0 0 1 1 1 0 0 H NH T FR 1 1 0 10 1 1 1 0 0 H NH 2+ 1 1 0 1 0 0 1 1 0 0 H NH 2− 1 0 0 1 0 0 1 1 0 0

When the pressure sensors 136, 138, 164, 166, 140, 278, 286, 146, 148,and 176 meet the normal operating conditions defined above, the valves142, 144, 168, 170, 130, 132, 160, 162, and 148 operate under theconditions defined in Table 4 below.

TABLE 4 Normal Valve States STATE STATE NAME LOGIC 142 144 168 170 130132 160 162 148 C NL 0 0 T01000000 TRIM — 1 0 0 0 0 0 0 C NL 1−T01100000 TRIM — 1 1 0 0 0 0 0 C NL 1+ T01101000 TRIM — 1 1 0 1 0 0 0 CNH T FR T01100010 TRIM — 1 1 0 0 0 1 0 C NH 2+ T00100010 TRIM — 0 1 0 00 1 0 C NH 2− T00101010 TRIM — 0 1 0 1 0 1 0 H NL 0 0 0T1011000 — TRIM 10 1 1 0 0 0 H NL 1− 0T1111000 — TRIM 1 1 1 1 0 0 0 H NL 1+ 0T1110000 —TRIM 1 1 1 0 0 0 0 H NH T FR 0T1111010 — TRIM 1 1 1 1 0 1 0 H NH 2+0T0111010 — TRIM 0 1 1 1 0 1 0 H NH 2− 0T0110010 — TRIM 0 1 1 0 0 1 0

Referring now to FIGS. 7-11, the hydraulic circuit 200 of transmission14 including components of the electro-hydraulic controller 16 isdisclosed. FIGS. 7-11 depict the status of the hydraulic circuit 200 inthe “H NL 0 0” state. FIG. 7 shows a pressure regulation and reliefportion 202 of the hydraulic circuit 200. The hydraulic circuit 200 isfed from a sump 204 that holds unpressurized hydraulic fluid which isdrawn from the sump 204 by a pump 206 which pressurizes the hydraulicfluid and feeds a main pressure line 208. As will be discussed infurther detail, main pressure line 208 feeds both 168 and 170 each ofwhich act on the main pressure line 208 to provide pressurized fluid tothe variator logic section 124 and the mode logic section 150.

A main relief valve 210 is coupled to the main pressure line 208 andprovides primary relief for the main pressure line 208 in over pressureconditions. The main pressure line 208 also feeds a main regulator 212which regulates the pressure of the hydraulic fluid and feeds a pilotpressure to the variator trim valves 142 and 144 on a regulated line246. The main regulator 212 also provides flow to a lubrication line 216that includes a cooler 218 and a filter 220. The lubrication line 216provides lubrication to the gears of the countershaft assembly 70 atgear lubrication 222 and to the variator 22 at variator lubrication 224.A lube regulator 226 receives hydraulic fluid from the lubrication line216 and controls the flow of fluid to the gear lubrication 222 andvariator lubrication 224. The cooler 218 cooperates with a cooler reliefvalve 232 so that the cooler relief valve 232 will prevent anover-pressure condition at the cooler 218.

Additional regulation and relief is provided by a main control reliefvalve 234 that cooperates with a control regulator 236 to provide aregulated pilot pressure in a pilot line 214 which provides a pilotpressure to assist in the actuation of the valves 142, 144, 168, 170,130, 132, 160, 162, and 148. In addition, a clutch backfill regulator238 maintains a proper back pressure on a mode backpressure line 240with the mode backpressure line further including a relief valve 242. Asa matter of convention, components in the electro-hydraulic controller16 including valves and regulators have one or more exhaust ports 244.Those exhaust ports are designated with reference to an exhaust 244which indicates that the ports 244 return to the sump 204, withoutpressurization.

A network shuttle 228 receives three inputs, a first mode logic inputline 282, a second mode logic input line 284, and a variator pressureline 230. The network shuttle 228 compares the pressures on each of thethree inputs and transfers the highest pressure input to the mainregulator 212. In state H NL 0 0, the second mode logic input line 284and the variator pressure line 230 have lower pressures than the firstmode logic input line 282 so that the first mode logic input line 282 isfed to the main regulator 212 to regulate the pressure on the mainpressure line 208. In other states, second mode logic input line 284 orthe variator pressure line 230 have the highest pressure and control themain regulator 212 and thereby control regulation of the main pressureline 208.

Referring now to FIG. 9, the mode trim control 152 is coupled to themain pressure line 208 with a port 270 of the first mode trim valve 168and a port 272 of the second mode trim valve 170 each coupled to mainpressure line 208. The first mode trim valve 168 is on when the state isH NL 0 0. In this state, the pilot line 214 is in communication with apressure sensor 278 associated with the first mode trim valve 168. Thepressure applied to pressure sensor 278 is sufficient to activatepressure sensor 278 to a value of 1, confirming the condition of thefirst mode trim valve 168 as stroked. When first mode trim valve 168 isstroked, the first mode logic input line 282 is pressurized. The firstmode logic input line 282 also communicates with the network shuttle 228as described above. The pilot line 214 communicates to both the firstmode trim valve 168 and the second mode trim valve 170. There is no flowof pressurized hydraulic fluid through 170 in H NL 0 0 and a second modelogic input line 284 since the second mode trim valve 170 is de-stroked.

In the mode logic section 150 the first mode logic input line 282 underthe H NL 0 0 state is in communication with first mode logic valve 160.When deactivated, the first mode logic valve 160 communicates the firstmode logic input line 282 to a portion of the second mode logic valve162 which is in communication with input clutch 46 so that the inputclutch 46 is stroked and active. However, neither the first mode clutch156 nor the second mode clutch 158 are stroked, so there is no motiontransferred through countershaft assembly 70.

Referring now to FIGS. 10 and 11, the hydraulic circuit associated withthe operation of the variator 22 is shown to include the endload chamber66 that operates with an endload relief valve 350 which is fed from thevariator control 120 by a variator control line 352 that is connected toa port 354. The endload relief valve 350 pressurizes the endload chamber66 but since the transmission 14 is in the H NL 0 0 state, there is noflow or pressurization of hydraulic fluid to the cylinders 184 a, 184 b,184 c, 186 a, 186 b, and 186 c. In the H NL 0 0 state, the countershaftassembly 70 does not receive rotation from the output 38 of the variator22, so the variator 22 experiences no torque.

The hydraulic schematic associated with the variator control 120 isshown in FIG. 8 where the pilot line 214 is in communication with eachof the valves 130, 132, 148, 142, and 144. In the H NL 0 0 state, thepilot line 214 is in communication with the pressure sensors 136 and 138so that the pressure on pilot line 214 is applied to the pressuresensors 136 and 138 to cause the state of the pressure sensors 136 and138 to be read as stroked or “1” by the processor 72. This allows theelectro-hydraulic controller 16 to confirm that the variator logicvalves 130 and 132 are in their proper state, which prevents pressurefrom being applied to the variator cylinders 184 a, 184 b, 184 c, 186 a,186 b, and 186 c.

Referring now to FIGS. 12 and 13, the other states of the mode trimvalves 168 and 170 are shown. When the second mode trim valve 170 isstroked, the pressure from pilot line 214 is sensed by the pressuresensor 286 and pressurized hydraulic fluid is communicated through thesecond mode logic input line 284. The pressure is varied to control thepressure to the second mode logic input line 284. Thus, under normaloperating conditions activation of the second mode trim valve 170 willresult in an active signal from pressure sensor 286.

As shown in FIG. 13, when the first mode trim valve 168 is deactivated,the pressure of pilot line 214 is not sensed by the pressure sensor 278.Similarly, the flow to first mode logic input line 282 is turned off sothat there is no pressurized hydraulic fluid transferred to first modelogic input line 282.

Referring now to FIGS. 14-16, the additional flow paths that areexperienced by the mode logic section 150 are depicted. Each of thefirst and second mode logic valves 160 and 162 are de-stroked in FIG. 9.In FIG. 14, the second mode logic valve 162 is stroked so that the firstmode logic input line 282 energizes the first mode clutch 156 throughthe port 302 on the second mode logic valve 162, while the input clutch46 is stroked by the main pressure line 208 through a port 386 on secondmode logic valve 162. The second mode clutch 158 is stroked from thesecond mode logic input line 284 through port 390 on the first modelogic valve 160 which feeds a port 392 which subsequently feeds a port388 on the second mode logic valve 162. The movement of the second modelogic valve 162 permits the pilot line 214 to communicate with thepressure sensor 166 so that the processor 72 can confirm that the secondmode logic valve 162 is operating correctly.

As shown in FIG. 15, when both mode logic valves 160 and 162 arestroked, the first mode clutch 156 is in communication with the firstmode logic input line 282 and the input clutch 46 is in communicationwith the main pressure in line 408 and the input clutch 46 is active asthere is no flow to the second mode clutch 158. The input clutch 46 isactivated from the main pressure line 208. Because the movement of thefirst mode logic valve 160 permits the pilot line 214 to communicate topressure sensor 164, the processor 72 can confirm that the first modelogic valve 162 is operating correctly.

As shown in FIG. 16, when the first mode logic valve 160 is stroked andthe second mode logic valve 162 is de-stroked, the first mode clutch 156is in communication with second mode logic input line 284 and secondmode clutch 158 is in fluid communication with first mode logic inputline 282. As will be discussed in more detail below, the use of the modetrim valves 168 and 170 with the mode logic valves 160 and 162 allowsthe electro-hydraulic controller 16 to compensate for single faultfailures of components in the mode control 122 without any loss offunctionality of the transmission 14.

Referring again now to FIG. 8, the operation of the variator control 120may best be understood by the inputs to the variator control 120 and theoutputs therefrom. It should be understood that the pilot line 214 is incommunication with every component of the variator control 120. Beyondthat, the basic input to the variator control is the regulated line 246which is fed from the main regulator 212. Under normal operation, thesecond variator trim valve 144 utilizes the regulated line 246 as asource of pressurized fluid and, responsive to a voltage signal from thecontrol circuit 76 and under the operation of the processor 72, controlsthe pressure applied to the cylinders 184 a, 184 b, 184 c, 186 a, 186 b,and 186 c of the variator 22. The pressure controlled hydraulic fluid istransmitted to the variator logic section 124 through a control line 400which feeds a damper 402 that provides the damped fluid flow through afirst variator logic input line 404. When both of the variator logicvalves 130 and 132 are stroked, the first variator logic input line 404is in communication with a variator control line 408 which feeds thenegative torque side 412 of the variator cylinders 184 a, 184 b, 184 c,186 a, 186 b, and 186 c.

In some cases, when the transmission 14 is in cold mode, the firstvariator trim valve 142 is active and the second variator trim valve 144is inactive. When the first variator trim valve 142 is active, the firstvariator trim valve 142 utilizes the regulated line 246 as a source ofpressurized fluid and, responsive to a voltage signal from the controlcircuit 76 and under the operation of the processor 72, controls thepressure applied to the cylinders 184 a, 184 b, 184 c, 186 a, 186 b, and186 c of the variator 22. The controlled pressure hydraulic fluid istransmitted to the variator logic section 124 through a control line 418which feeds a damper 416 that provides the damped fluid flow through asecond variator logic input line 418. When both of the variator logicvalves 130 and 132 are stroked, as shown in FIG. 8, the second variatorlogic input line 418 has no flow path. Thus, it is necessary that thestate of the variator logic valves 130 and 132 be changed in coldoperation. The first variator trim valve 142 operates at a pressure thatis higher than the second variator trim valve 144 to compensate for thehigher viscosity of the fluid used in the variator 22.

A variator shuttle 420 is operable to change the flow path from thevariator pressure line 230 between the control line 418 and the controlline 400. The variator pressure line 230 is in communication with thenetwork shuttle 228 and a transducer 422. The transducer 422 is incommunication with the processor 72 and is operable to provide a signalindicative of the pressure in the respective control line 418 or 400 toprovide feedback to the processor 72 for control of the first and secondvariator trim valves 142 and 144. The first and second variator trimvalves 142 and 144 apply the appropriate pressure to the cylinders 184a, 184 b, 184 c, 186 a, 186 b, and 186 c based on the pressure in therespective control line 418 or 400. For example, a sudden change inpressure as sensed by the transducer 422 is indicative of a change inload on the output 38 of the variator 22, which signals the processor 72of the electro-hydraulic controller 16 to modify the pressure applied orswitch between pressurization of the first and second sides of thecylinders 184 a, 184 b, 184 c, 186 a, 186 b, and 186 c.

Effectively, the variator logic section 124 switches the direction ofpressure applied to the cylinders 184 a, 184 b, 184 c, 186 a, 186 b, and186 c by switching between applying pressure to the variator control 408and another variator control line 410. The reversal of the direction ofthe pressure applied between the positive torque side 356 and thenegative torque side 412 permits the cylinders 184 a, 184 b, 184 c, 186a, 186 b, and 186 c to precesses to an equilibrium position. A pair ofcheck valves 430 and 432 cooperate to prevent improper flow of hydraulicfluid to the endload chamber 66. The check valves 430 and 432 act toallow the pressurized control line, either control line 408 or 410, toapply pressure to the endload chamber 66 while the load is applied tothe cylinders 184 a, 184 b, 184 c, 186 a, 186 b, and 186 c by overcomingthe pressure limit of the respective check valve 430 or 432.Simultaneously, the opposite check valve 432 or 430 prevents flowthrough the valve 430 or 432 in the wrong direction. An endload shuttle434 prevents improper flow on the return side of the cylinders 184 a,184 b, 184 c, 186 a, 186 b, and 186 c. For example, if the pressure inthe control line 408 is higher than the pressure in the control line410, the check valve 430 will crack permitting the pressure to beapplied to the endload chamber 66 and the endload relief 350. Theendload shuttle 434 shifts to the positive torque side 356 to preventflow from the positive torque side 356 to the endload chamber 66.

Referring now to FIGS. 17-19, the various logical results of thedifferent states of the variator logic valves 130 and 132 are disclosed.When the first variator logic valve 130 is stroked and the secondvariator logic valve 132 is de-stroked, the first variator logic inputline 404 is in communication with the variator control line 410. Thisarrangement of the first and second variator logic valves 130, 132pressurizes the positive torque side 356 of the cylinders 184 a, 184 b,184 c, 186 a, 186 b, and 186 c and the second variator logic input line418 has no flow. The variator control line 352 is in communication withthe variator control line 408 that pressurizes the negative torque side412 as shown in FIG. 17. When the first variator logic valve 130 isde-stroked and the second variator logic valve 132 is stroked, line 418communicates with line 410 and line 352 communicates with line 408 asshown in FIG. 18. When both valves 130 and 132 are de-stroked line 418communicates with line 408 and line 404 does not have a flow path. Thevariator control line 352 communicates with line 410 as shown in FIG.19. Thus, a failure of either of the variator logic valves 130 or 132can be resolved with the redundant use of the second of the variatorlogic valves 130 or 132.

In operation, the transmission 14 has three distinct operating modes:mode 1 is a low speed IVT mode when the transmission 14 operates between10 miles per hour in reverse and 10 miles per hour in forward with ageared neutral; mode 2 is a high speed forward CVT mode for speeds inexcess of 10 miles per hour, mode 3 is a transition mode providing for atransition between the IVT (mode 1) and CVT (mode 2). Referring to FIG.6, the present implementation provides for six potential responses to asingle fault failure of a component of the electro-hydraulic controller16. Depending on the direction of torque, the responses must maintainfull functionality of the transmission 14 in spite of the fault. Bycomparing the expected states of the pressure sensors 136, 138, 164,166, 140, 278, 286, 146, 148, and 176 to the actual states, faults aredetected in the electro-hydraulic controller 16. Redundancy in thehardware permits the functionality of the transmission 14 by alteringthe fluid flow path using other components in the electro-hydrauliccontroller 16 to compensate for the fault.

Referring to FIG. 23, a table shows the potential fault states ofvarious components of the electro-hydraulic controller 16 in the firstcolumn. Across the top of the table are the normal states that thetransmission 14 may experience under normal, hot, operating conditions.Each response of the electro-hydraulic controller 16 that resolves thesingle faults listed in the first column are shown in the table, where aresponse is necessary. When the transmission 14 is operating in a coldmode and experiences faults, the fault response is as shown in the tableof FIG. 24.

The ability of the electro-hydraulic controller 16 to respond to singlepoint failure modes without loss of functionality is a significantimprovement over the prior art systems that fail to neutral or fail to aparticular mode allowing the vehicle 8 to “limp” home. The redundancy ofthe electro-hydraulic controller 16 that results from the interaction ofthe variator control 120 and the mode control 122, permits components,such as valves, that are dedicated to a specific purpose to be used toresolve failures in other areas of the transmission 14, without loss offunctionality.

In a second embodiment, shown in FIGS. 20-21, an electro-hydrauliccontroller 516 of a transmission 514 is similar to electro-hydrauliccontroller 16, with mode logic section 150 omitted and replaced with amode logic section 550 having three mode logic valves 552, 554, and 556.The mode logic section 550 controls the input clutch 46, a first modeclutch 156, a second mode clutch 158, and a third mode clutch 558. Thecountershaft assembly 570 of the transmission 514 includes a third modeto increase the range of the transmission 514. This requires that themode logic section 550 provide sufficient logic to vary the operation ofthe clutches 46, 156, 158, and 558 to achieve all three modes oftransmission 514 as well as the transition between modes. In all otherrespects, the transmission 514 is similar to transmission 14 and likereference designators will be used where appropriate.

The first mode logic input line 282 and the second mode logic input line284 each feed the second mode logic valve 554 of the mode logic section550. Each of those lines 282 and 284 may be pressurized independently,providing four different states for the mode logic section 550. As notedin Table 5 below, there are eight distinct modes used to operate theclutches 46, 156, 158, and 558 to achieve the desired clutch states tooperate the transmission 514. The remaining normal states are controlledby changing the states of the valves 552, 554, and 556 as described inthe Table 5 below.

TABLE 5 Three Mode Clutch Control Normal States Input States ClutchStates Input Input Valve Valve Valve Input Mode Mode Mode Line 282 Line284 552 554 556 Clutch 1 2 3 0 0 0 0 0 0 0 0 0 1 0 0 0 0 1 0 0 0 0 0 0 11 1 0 0 0 1 0 0 1 1 1 1 0 0 1 1 0 1 1 1 1 1 0 0 1 0 1 1 1 0 1 1 1 1 0 10 11  0 1 1 1 0 0 1 0 1 0 0 1

FIG. 20 shows the first state of the logic valves 552, 554, and 556where each is de-stroked. When the first logic mode input line 282 ispressurized, the input clutch 46 is stroked. Under some operatingconditions, the input clutch 46 may also be stroked when the secondlogic valve 554 is stroked, with the input clutch 46 being placed influid communication with main pressure line 208 as shown in FIG. 21.

Also, as shown in FIG. 20, when all of the logic valves 552, 554, and556 are de-stroked, the first mode clutch 156 is in communication withthe second mode logic input line 284 such that when the second modelogic input line 284 is pressurized, the pressure is transferred to thefirst mode clutch 156 to activate the first mode clutch 156.

In FIG. 21, both logic valves 554 and 556 are stroked so that the secondmode clutch 158 is in communication with second mode logic input line284 and is stroked when second mode logic input line 284 is pressurized.The first mode clutch 552 is in communication with first mode logicinput line 282 so that pressurization of the first mode logic input line282 energizes the first mode clutch 552. In this condition, the inputclutch 46 is put in communication with the main line 208 which activatesthe input clutch 46.

Finally, as shown in FIG. 22, only the second logic valve 554 is strokedso that the second mode clutch 158 maintains communication with thesecond mode logic input line 284 and is stroked when the second modelogic input line 284 is pressurized. The input clutch 46 maintainscommunication with the main line 208 and the third mode clutch 558 isplaced in communication with the first mode logic input line 282 and isstroked when the line 282 is pressurized.

Each of the mode logic valves 552, 554, and 556 have a respectivepressure sensor 562, 564, 566 that is operable to detect when anassociated valve is stroked by sensing the pressure of the pilot line214. As described above with regard to the pressure sensors 136, 138,164, 166, 140, 278, 286, 146, 148, and 176, the pressure sensors 562,564, 566 are illustratively pressure switches, but could be pressuretransducers in other embodiments.

A control circuit 576 includes a first driver 610 powering the firstvariator trim valve 142 and the first mode trim valve 168; a seconddriver 612 powering the second variator trim valve 144 and the secondmode trim valve 170, as well as the boost valve 178; a third driver 614powering the first mode logic valve 552, the first variator logic valve130, and the third mode logic valve 556; and a fourth driver 616powering the second variator logic valve 132 and the second mode logicvalve 554. The drivers 610, 612, 614 and 616 are each potential failurepoints that are addressed in the tables shown in FIGS. 25 and 26.

In mode 1, the transmission 514 operates as an infinitely variabletransmission from reverse, through neutral, up to forward speeds ofabout 20 miles per hour. In mode 2, the transmission 514 operates as acontinuously variable transmission from speeds of about 20 miles perhour to about 45 miles per hour. In mode 3, the transmission 514operates as a continuously variable transmission with speed of 45 milesper hour and above.

Because of the redundancy of the mode logic valves 552, 554, and 556,the transmission 514 is single fault tolerant with alternate modes ofoperation similar to those described above with regard to transmission14. The state name convention for the second embodiment has threeaspects including a variator state, a clutch state, and a servo state.Table 6 shows the key for the first aspect, the variator state.

TABLE 6 Variator State Codes CODE DESCRIPTION C Normal Cold H Normal HotAC Alternate Cold F Variator Logic Valve 132 Fault

Table 7 shows the key for the second aspect, the clutch state.

TABLE 7 Clutch State Codes Code Description Active Clutches NN NormalNeutral None NTS Normal Start 46 N0 Normal Mode 0 46 N1 Normal Mode 146, 156 N12 Normal 1-2 Transition 46, 156, 158 N2 Normal Mode 2 46, 158N23 Normal 2-3 Transition 46, 158, 558 N3 Normal Mode 3 46, 558 ANAlternate Neutral None ATS Alternate Start 46 A0 Alternate Mode 0 46 A1Alternate Mode 1 46, 156 A12 Alternate 1-2 Transition 46, 156, 158 A2Alternate Mode 2 46, 158 A23 Alternate 2-3 Transition 46, 158, 558 A3Alternate Mode 3 46, 558 F3L Fault Valve 168 Low 46, 156 F4L Fault Valve170 Low 46, 156

Table 8 shows the key for the third aspect, the side of the cylinders184 a, 184 b, 184 c, 186 a, 186 b, and 186 c which are pressurized.

TABLE 8 Servo State Codes Code Direction 0 None S1 Negative Torque Side412 S2 Positive Torque Side 356

Referring now to FIGS. 25 and 26, the response for specific single faultfailures of components of the electro-hydraulic controller 16 in thesecond embodiment are shown. The failure mode is shown in the firstcolumn Expected states are shown across the top of the remaining columnswith the response state shown in the table. Where blanks are shown inthe table, there is no response required as the single fault failuredoes not have an impact on the operation of the electro-hydrauliccontroller 16.

Although certain illustrative embodiments have been described in detailabove, variations and modifications exist within the scope and spirit ofthis disclosure as described and as defined in the following claims.

1. A transmission comprising a variator including an input and anoutput, a countershaft assembly operatively coupled to the output of thevariator, an electro-hydraulic controller including a variator trimsection, a variator logic section, a plurality of double-actingcylinders for varying the ratio through the variator, and a transducerfor measuring a pressure in a hydraulic fluid path from the variatortrim section to the variator logic section, the variator trim sectionincluding a first variator trim valve assembly operable to control thepressure of the hydraulic fluid path under a first operating conditionand a second variator trim valve assembly operable to control thepressure of the hydraulic fluid path under a second operating condition.2. The transmission of claim 1, wherein the variator logic sectionincludes a first variator logic valve assembly and a second variatorlogic valve assembly, the first and second logic valve assembliescooperating to define a first hydraulic fluid path under the firstoperating condition and a second hydraulic path under the secondoperating condition.
 3. The transmission of claim 2, wherein the firstvariator logic valve assembly maintains a constant position during thefirst operating condition of the transmission.
 4. The transmission ofclaim 3, wherein the second variator logic valve assembly maintains aconstant position during the second operating condition of thetransmission.
 5. The transmission of claim 4, wherein the first variatorlogic valve assembly moves between a first position and a secondposition during the second operating condition of the transmission tovary the fluid flow path between a first side and a second side of thedouble-acting hydraulic cylinders.
 6. The transmission of claim 4,wherein the second variator logic valve assembly moves between a firstposition and a second position during the first operating condition ofthe transmission to vary the fluid flow path between a first side and asecond side of the double-acting hydraulic cylinders.
 7. Thetransmission of 4, wherein the first operating condition is a normaltemperature condition and the second operating condition is a coldtemperature condition.
 8. The transmission of claim 7, wherein thesecond variator trim valve assembly provides hydraulic fluid at a higherpressure than the first variator trim valve to provide a higher pressureto the variator during the second operating condition.
 9. Thetransmission of claim 8, wherein the variator logic section includes athird variator logic valve assembly that is moveable between a firstposition and a second position wherein the third variator logic valveassembly defines a hydraulic fluid path that boosts the pressure appliedby the first variator trim valve in the second operating condition inthe event the second variator trim valve fails.
 10. The transmission ofclaim 8, wherein the torque applied by the variator is limited in thesecond operating condition.
 11. An electro-hydraulic controller for atransmission including a variator having an output, theelectro-hydraulic controller comprising a variator trim sectionincluding a plurality of variator trim valve assemblies each operable tocontrol the pressure in a hydraulic fluid supplied to the variator, avariator logic section including a plurality of variator logic valveassemblies each movable between a plurality of positions to define aflow path for the hydraulic fluid to the variator, a plurality ofpressure switches, a transducer, a plurality of speed sensors operableto measure the speed of various components of the transmission aprocessor operatively coupled to the variator trim valve assemblies, thevariator logic valve assemblies, the plurality of pressure switches, thetransducer and the speed sensors, and a memory device includinginstructions that, when executed by the processor, cause the processorto control the variator trim valve assemblies and variator logic valveassemblies in response to signals received from the pressure sensors,the transducer, and speed sensors to control the ratio of the variator.12. The electro-hydraulic controller of claim 11, wherein the variatortrim section includes a normal mode variator trim valve assembly and acold mode variator trim valve assembly.
 13. The electro-hydrauliccontroller of claim 12, wherein the cold mode variator trim valveassembly develops a pressure in the hydraulic fluid that issubstantially higher than the normal mode variator trim valve assembly.14. The electro-hydraulic controller of claim 13, wherein the memorydevice includes further instructions that, when executed by theprocessor, define a first fluid path when the normal mode variator trimvalve assembly is active and a second fluid path when the cold modevariator trim valve assembly is active.
 15. The electro-hydrauliccontroller of claim 14, wherein the memory device includes furtherinstructions that, when executed by the processor, define a third fluidpath when the cold mode variator trim valve assembly is active and theprocessor determines, based on signals from the pressure switches, thatthe cold mode variator trim valve assembly is in a fault condition. 16.The electro-hydraulic controller of claim 15, wherein the third fluidpath supplies hydraulic fluid with a boosted base pressure to the normalmode variator trim valve.
 17. The electro-hydraulic controller of claim11, wherein the variator logic valve section defines a first fluid flowpath under normal operating conditions, a second fluid flow path undercold operating conditions, and a third fluid flow path if a variatortrim valve assembly fails during cold operating conditions.
 18. Theelectro-hydraulic controller of claim 17, wherein the memory deviceincludes further instructions that, when executed by the processor,process the signals from the speed sensors to determine a torque appliedto the output of the variator, and depending on the direction of thetorque applied to the output of the variator, modify the operation ofthe variator logic valve assemblies to modify the first, second, orthird fluid paths to operate the variator.
 19. The electro-hydrauliccontroller of claim 18, wherein the variator logic section includes atleast one variator logic valve assembly movable between two positions toapply a positive pressure to first and second sides of the variator,depending on the torque applied to the output of the variator.
 20. Theelectro-hydraulic controller of claim 19, wherein the variator logicsection includes a boost valve that is operable to move between firstand second positions to provide a boosted pressure to the variator trimsection if one of the variator trim valve assemblies fails during coldoperating conditions.